posted 02-26-2012 07:00 PM ET (US) I am considering replacing my MIRAGEplus 17P propeller with a four-blade Stiletto Bay Pro 111 propeller. My Mercury EFI 150-HP can turn 5,800-RPM with the MIRAGEplus. Would I be able to replace the MIRAGEplus 17P with a Stiletto Bay Pro 17P or will this be too much pitch when changing to a 4 blade?

aussiejake

posted 02-26-2012 07:02 PM ET (US)
I should also mention Mercury suggest the Mercury EFI 150 hp should be propped to achieve between 5000rpm and 5750rpm.

Tom W Clark

posted 02-28-2012 09:46 AM ET (US)
Without explaining to us what Whaler the Mercury EFI 150 is on and how the motor is mounted it, no useful advice can be offered.

What year is your Mercury EFI 150?

What gear ratio does it use?

aussiejake

posted 02-28-2012 05:01 PM ET (US)
The Mercury EFI 150hp is a 2006 model. The gear ratio is 1.87:1. The boat is a not a whaler but a fibreglass 19 foot half cabin with a 22 degree V. The motor is mounted 3 holes up with the anticavitation plate just being splashed when on the plane and trimmed out.

At present the MIRAGEplus allows the motor to reach 5800rpm on calm water and trimmed out. I am trying to achieve a smmother transition to plane and being able to hold a slower plane speed due to having small children on the boat. From reading articles I came to the conclusion a four-blade propeller would achieve what I am after, so I thought I would ask if anyone had experience changing from a MIRAGEplus propeller to a four-blade propeller. We do not have the luxery of being able to loan and test propellers were I live, so I would have to purchase one and hope it works to my expectations.

Owtrayj25

posted 02-28-2012 06:15 PM ET (US)
My experience in moving from an [unclear] a four-blade REVOLUTION4 was that I lost about 300-RPM and a slight amount off of the top end. I noticed a slight decrease in planing RPM and definite increase in stern lift. This was on a larger V6 than your 150. The REVOLUTION4 is a heavy propeller and also had an increase in shift clunk, which can now be mitigated with newer FLO-TORQ IV hub. Not sure of the wieght of the Stilleto [compared to] the REVOLUTION4 . Perhaps someone else has first- hand experience with a smaller V6. If comparable to the REVOLUTION4 I would surely try to test it out before investing in a purchase....

Owtrayj25

posted 02-28-2012 07:06 PM ET (US)
Make that FLO-TORQ IV.

aussiejake

posted 02-28-2012 08:55 PM ET (US)
Thank you for the reply Owtray.

I am assuming the REVOLUTION4 was the same pitch as the MIRAGEplus it replaced.

If my RPM were lowered by 300-RPM it would still keep me well with the recommended engine speed range. I will wait and see if anyone has had experience with the Stiletto Bay Pro III 4 blade. I have read the REVOLUTION4 has very large blade areas similar to the MIRAGEplus and is recommended for larger vessels.

I will be using a FLO-TORQ IV for whatever propeller I use. Ceers,Jake

L H G

posted 02-29-2012 01:18 AM ET (US)
I would recommend either a four-blade Vensura or a three-blade Enertia. I agree that a REVOLUTION4 is a little too much prop for the engine and application.

Tom W Clark

posted 02-29-2012 10:05 AM ET (US)
There is a lot more to propellers than just the number of blades. You cannot talk generally about four-blade propellers in any meaningful way. The four blade Mercury REVOLUTION4 and the four blade Mercury VenSura (Offshore) are very different props. I do not recommend a VenSura for this application.

If the goal is lower planing sped, the REVOLUTION4 is a good prop to use. Yes, you will loose about 200-300 RPM going from a MIRAGEplus to a REVOLUTION4 of the same pitch. The 2006 Mercury 150 EFI is more than capable of handling a REVOLUTION4 . You may opt to use either the Flo-Torq III or the Flo-Torq IV if the shift clunk is bothersome and there WILL be significant shift clunk.

The Mercury Enertia is worth trying too and it is available in one inch pitch increments which makes finding the right pitch easier, however you state you do not have an easy way to experiment so that may not be of use.

I have no personal experience with the Stiletto bay Pro III 4.75 and I don't know anybody who does so I cannot offer any advice there. My intuition is that it would not be a good fit on your boat being designed for larger boats than yours.

If you want a Stiletto, try the three blade Advantage 4.75 and raise the motor another set of bolt holes.

sosmerc

posted 02-29-2012 11:38 AM ET (US)
The Merc Alpha 4 would be a much cheaper way to find out if a four-blade will meet your needs. There is a 16 pitch available, and that might be the ticket. It should keep the boat on plane at a lower rpm.

Tom W Clark

posted 02-29-2012 11:48 AM ET (US)
The Mercury Alpha 4 is by far the worst four blade propeller I have ever tried. Do not waste your money on one. It is like a really bad version of the VenSura. The three blade aluminum Mercury BlackMax is a much better prop than the Alpha 4.

L H G

posted 02-29-2012 02:00 PM ET (US)
I tried a REVOLUTION4 on a 19-foot boat with a 150 Merc. It was not a good combination at all. Actually, it was terrible. It's a lot of prop for a 2.5 liter engine to handle.

In four-blades, the four-blade Vensura is a much better prop for a single 150 on a heavier boat. Mine performed quite well, and I know others enjoying the same good performance with 150-HP on a deeper-V 19-foot boat. It is a good load carrying prop. It won't be as fast top end as an Enertia, but it sounds like for this application speed doesn't matter.

If it is difficult to test props Down Under, an Enertia is always a safe investment. They were designed to be an improvement over the MIRAGEplus for outboard applications below 23" pitch. They are the latest technology and perform well, which is why they cost more. Boston Whaler generally uses them on most single engine applications.

Perry

posted 02-29-2012 04:58 PM ET (US)
I have an Enertia on a 19-foot Boston Whaler and it is one of the best props I have tried and I have tried many different three-blade and four-blade props.

It provided good acceleration and top speed as well as excellent grip in rough seas.

aussiejake

posted 02-29-2012 06:51 PM ET (US)
Thank you all for the valuable input.

I will make a decision and report back with a comparison from the MIRAGEplus 17P to whatever I decide to replace it with.

cheers

sosmerc

posted 02-29-2012 07:25 PM ET (US)
I have personal experience with the Enertia and agree that it is a great prop, but I thought we were limiting ourselves to four-blades. I have run the four-blade Alpha 4 aluminum on several of my customers boats and it was fine. However, we are talking large heavy Bayliner Trophy models, which frankly, aren't going to be great performing hulls no matter what prop is on. (I am talking older 90's vintage Trophy with forward cabins that are heavy). It would take a lot of power to really get the bow up.

Too bad that it appears Mercury is not going to bring out the four-blade Spitfire series for V6 engines. I am running one on my little 15 Whaler with Merc F50 and it seems to be a good prop.

jimh

posted 03-01-2012 12:39 PM ET (US)
I do not recall seeing any first-hand test data from a classic Boston Whaler boat where both a Mercury MIRAGEplus and a Mercury ENERTIA propeller were tested and compared under the same conditions. Is there any such data available? I know there are a lot of mentions of the ENERTIA being an improved propeller, but that is just what Mercury's marketing literature says. I would find it more interesting to see some actual test data that an owner of a classic Boston Whaler boat has collected from his own testing.

Perry

posted 03-01-2012 10:13 PM ET (US)
I have tested both on my Whaler but because it is not a "classic" Whaler I guess it is of no significance in this discussion.

jimh

posted 03-01-2012 10:25 PM ET (US)
Perry--Have you published the propeller test data? You're making too much out of the word "classic."

sosmerc

posted 03-03-2012 11:47 AM ET (US)
Looking back over my log records, I ran 4 mph faster when switching from a 17 pitch Black Max to a 17 pitch Enertia.This was on a 1998 18ft. Ventura with 1998 135 Optimax.Went from 42 mph to 46 mph....verified by GPS. Engine was in second hole, one passenger, light load of fuel and bimini top up.

The boat was very quick to plane and held plane at low speeds, which is what I was hoping for.

Fuel economy was terrible compared to the MIRAGEplus, but could be due to the Stiletto being too much pitch.

An example of the fuel economy difference,

MIRAGEplus 3200rpm 1.8 km per litre at 26 litres per hour.

Stiletto 3200rpm 1.3 Km per litre at 33 litres per hour.

I am considering raising the motor another set of holes but I dont think I will gain any more than an extra 150rpm and I doubt the fuel economy will improve much.

Looks like the MIRAGEplus is better match to my hull.

tmann45

posted 03-10-2012 10:33 PM ET (US)
What were your speeds with those two props at 3200 rpm?

aussiejake

posted 03-11-2012 05:13 AM ET (US)
Both propellers held the boat on around 45kph at 3200rpm.

Today I have raised the motor to the last set of holes. Hopefully I can re-test next weekend.Even the MIRAGEplus will be able to handle the higher motor as it does not lose grip even when fully trimmed out.

I will be carefully monitoring water pressure though.

All data is gathered from Smartcraft.

sosmerc

posted 03-11-2012 08:13 PM ET (US)
Those numbers don't jive for some reason. 45mph @ only 3200 rpm with a 17 pitch prop and 1.87 gear ratio is not theoretically possible. 45mph must have been at a much higher rpm.

aussiejake

posted 03-12-2012 01:30 AM ET (US)
Sorry Sosmerc I wasnt really looking at the speed I was mostly comparing km per litre and fuel flow, but I did check today.

I raised the motor to the highest holes and managed to get back out today with the Stiletto Bay Pro III 17P.

Achieved 5320 rpm at wide WOT, speed was 74.4kph on GPS.

Fuel economy went to 1.5 litres per km at 3000 rpm.

Still not as good as the MIRAGEplus.

The MIRAGEplus achieves 75kph at 5800rpm.

Speeds at 3200rpm were 42kph. (gps)

I will put the MIRAGEplus on for next weekend and see how it performs with the raised motor.

The Stiletto Bay Pro III seems to have a lot of grip, I assume this has to do with the aggressive cupping?

74.4 KPH at 5320 RPM with a nominal 17 inch pitch propeller turned through 1.87:1 gears yields about negative one percent (-1%) slip, which is very typical for the Stiletto Bay Pro 4.75 (III). I see nothing odd there.

L H G

posted 03-12-2012 05:09 PM ET (US)
Negative slip is impossible. Depending on the brand of the prop, you have to add 1" or 2" in pitch, maybe even 3", for the cupped edge. That will produce a positive slip calculation. Cupping increases effective pitch. The slip formula is based on pitch of an uncupped blade.

aussiejake

posted 03-12-2012 05:30 PM ET (US)
The RPM was taken off Smartcraft and the speed was checked on GPS and Smartcraft pitot which has been calibrated.

I would confirm Toms initial comments of the Stiletto Bay Pro III being made for larger boats was correct.

But it is the smoothest running propeller I have tested, eliminating all vibrations at any RPM and a perfect transition to plane.A 15P would possibly have been a better fit for my boat.

aussiejake

posted 03-12-2012 05:36 PM ET (US)
LHG, I did comment earlier that the Stiletto Bay Pro III 17P was more like a 19P propeller. I substituted the 17P for 19P in the propeller slip calculator and it came up with 9.71% slip which is more acceptable than -1%.

The motor originally came with a 19P Laser propeller when it was installed and it would only reach 5350rpm at WOT.